Processes and compositions for converting zero valent metals photographic images to formazan dye images

ABSTRACT

A zero valent metal image in which the metal has a standard oxidation potential more positive than -0.98 volt is advantageously replaced by a formazan dye by the single process step of contacting the metal image with a solution of a ligand in the presence of a tetrazolium salt when the combination of tetrazolium salt and ligand with water and zero valent metal produces a solution reaction potential E greater than +0.01 volt, the process forming a good dye image when the formazan dye is nondiffusible and the process blixing the metal image when the formazan dye is diffusible and the metal-ligand complex is diffusible. Compositions of tetrazolium salt and ligand are advantageously used in this single step process for dye image formation or for blixing a metal image.

United States Patent Brault et a1.

[54] PROCESSES AND COMPOSITIONS FOR CONVERTING ZERO VALENT METALS PHOTOGRAPHIC IMAGES TO FORMAZAN DYE IMAGES [72] Inventors: Albert T. Brault, Rochester; Vernon L.

Bissonette, Brockport, both of N.Y.

[73] Assigneez Eastman Kodak Company, Rochester,

[51] Int. Cl. ..G03c 5/24, G03c 5/44 [58] Field ofSearch ..96/60 R,6OBF, 48,51

[56] References Cited UNITED STATES PATENTS 3,503,741 3/1970 Wilson etal ..96/20 3,414,411 12/1968 Micheletal.

[ Feb. 15, 1972 FOREIGN PATENTS OR APPLICATIONS 670,883 4/1952 Great Britain ..96/54 Primary Examiner-Norman G. Torchin Assistant Examiner-Alfonso T. Suro Pico Attomey-W. H. J. Kline, J. R. Frederick and R. C. Livermore [57] ABSTRACT A zero valent metal image in which the metal has a standard oxidation potential more positive than -0.98 volt is advantageously replaced by a formazan dye by the single process step of contacting the metal image with a solution of a ligand in the presence of a tetrazolium salt when the combination of tetrazolium salt and ligand with water and zero valent metal produces a solution reaction potential E greater than -0i0l volt, the process forming a good dye image when the formazan dye is nondiifusible and the process blixing the metal image when the formazan dye is diffusible and the metal-ligand complex is diffusible. Compositions of tetrazolium salt and ligand are advantageously used in this single step process for dye image formation or for blixing a metal image.

20 Claims, No Drawings PROCESSES AND COMPOSITIONS FOR CONVERTING tions comprising (l) a tetrazolium salt (T-salt), (2) a ligand ZERO VALENT METALS PHOTOGRAPIIIC IMAGES TO which forms a soluble and diffusible metal complex, (3) water FORMAZAN DYE IMAGES and (4) a zero valent metal that has a standard oxidation potential morepositive than O.98 volt such that our combination produces a solution reaction potential E of at least +0.01 volt. The components in our novel combination react to produce a formazan dye and a metal compound that is in equilibrium with a very low concentration of the metal ions. In one embodiment of our invention, substantially all of a metal image is converted to (i.e., replaced by) a nondiffusible formazan dye image by contacting said metal image with an aqueous solution of a ligand that forms a soluble and diffusible metal complex in the presence of a T-salt and substantially all of the metal image is complexed without the need for a separate bleach step followed by a washing step and a separate fix step as is required by the prior art. Our process can advantageously be used to replace at least a part or all of a metal image with a formazan dye image. Water-soluble and diffusible T-salts (i.e., a T-salt whose solution will pass freely to said metal image when it is in a colloid layer) are advantageously included the same aqueous solution with said ligand.

This invention is related to photography, compositions for 5 use in photographic processing, photographic processes for forming dye images and processes for the removal of metal images and metal salts from a color-developed color photographic l ment. 7

In the photographic processing of certain color photo- 10 graphic elements, silver images and dye images are formed during the color development step or steps, and it is desired to, remove the silver image and any residual silver halide so that the processed element will contain only the dye images and will not be subject to the formation of printout of silver from residual silver halide upon prolonged exposure to viewing light. The silver image is usually bleached, i.e., converted to a silver salt by treating it, for example, with a solution of alkaline metal ferricyanide in the presence of bromide ions, and then subsequently treating the silver salt with a silver salt complexing agent, such as an alkaline metal thiosulfate solution to convert the silver salt into a water-soluble, diffusible complex which is readily removed by washing the photographic element; 25

Alternatively, the silver andresidual silver halide can be removed by using a blix, i.e., combined bleach-fix solution. Farmers Reducer, formed by combining a solution of watersoluble ferricyanide and a water-soluble thiosulfate, is a strong blix; however, it has a very short life and, for this reason, is not practical for many color processing applications. Other wellknown blixes use, as an oxidizing or bleaching agent, a ferric ion EDTA complex with a thiosulfate fixing agent. Although E (EM- M Formf-ult) this type of blix is. quite effective in removing the silver and 59 silver halide from the color-processed element, it is quite 35 frequently necessary to use a separate bleach bath in addition to the blix in order to insure that leuco forms of certain dye images formed during color processing are completely converted to the colored or dye form. It is therefore desirable to provide other blix compositions which are stable and which can be used without the necessity of having a separate bleach ha h British Pat. No. 908,299 describes a process for converting a silver image in a photographic emulsion layer into a formazan dye image by treating the silver image with a tetrazolium salt in the presence of cyanide ions, and subsequently bleaching with a ferricyanide bromide bleach bath, followed by washing, fixing with a sodium thiosulfate bath, washing and drying. The use of cyanide ion is very undesirable because of 50 the danger to the operating personnel. Furthermore, the process described by the British patent requires a separate, additional bleach, fix and three intermediate washing steps in order to remove the silver image left after forming the formazan dye image.

In another embodiment of our invention, compositions comprising (1) a water-soluble and diffusible T-salt that is reduced by metal to form a water-soluble and diffusible formazan dye and (2) a water-soluble and diffusible metal complexing agent that forms a water-soluble and diffusible metal complex, are dissolved in water to make blix solutions that are valuable for removing silver and silver halide from colordeveloped color photographic elements.

The solution reaction potential E is defined as follows:

in which a and b are each integers of from 1 to 3 determined by the stable oxidation state of metal ion and which are needed to satisfy the stoichiometric relationship of the reaction of metal with T-salt; d represents the number of electrons transferred in said reaction;

are the standard oxidation potentials for (1) zero valent metal to metal ion of valence m and (2) formazan dye to T-salt, respectively, [m"' [Formazan], [T-salt] and [11*] represent the concentrations of the indicated material. Standard oxidation potentials are for unit activity at 25 C. as referred to the hydrogen-hydrogen ion couple as zero volts. (See Handbook of Chemistry & Physics, 41st Edition, page 1,733 1959).)

The water-soluble, diffusible tetrazolium salts used to advantage according to our invention, are represented by the follquias stnsla iw It is therefore an object of our invention to provide a novel e i e blix composition which is stable and is valuable for use in 1 I (X color photographic processing. N

Another object of our invention is to provide a novel process for removing silver and residual silver halide from a 9 9P? pl etsstsnh ssla sut.. ..W... Q

Another object of our invention is to provide a novel process for converting a metalimage to a formazan dye image and, simultaneously, to remove the metal image from a blackand-white d ys snsqpb tqseahieslsmsma I I,

Still another ob ect of our invention 18 to provide a novel composition which is valuable for the conversion of a silver image into a formazan dye image and, simultaneously, to remove the silver image in a single processstep.

6 9 R3lNl-I?'R1 R3I||I-IIIR1 2(X )n--! N I Still other objects of our invention will become apparent from a consideration of th !lsuinsspswifis iqqand shims;

wherein R, and R each represent a group such as an aryl These and still other objects of our invention are accomgroup, a phenyl group (e.g., phenyl, tol'yl, butylphenyl, a plished by the preparation and use of of our novel combinahydroxyphenyl group, an alkali metal or ammonium salt of Carboxyethylphenyl, a carboxyethylphenyl group, an ethoxycarbonylphenyl group, an aminophenyl group, a carbamylphenyl group, a sulfoethylphenyl group, an alkali metal or ammonium salt of a sulfophenyl group, a sulfonamidophenyl group, a sulfamylphenyl group, a mercaptophenyl group, a nitrophenyl group, etc.), a naphthyl group (e.g., a-naphthyl, B-naphthyl, a carboxynaphthyl group, a hydroxynaphthyl group, a sulfonaphthyl group, a mercaptonaphthyl group, an aminonaphthyl group, a carbamylnaphthyl group, a sulfonamidonaphthyl group, a sulfamylnaphthyl group, a nitronaphthyl group, etc.) etc., and a heterocyclic group, preferably containing from five to six atoms, and preferably containing hereto atoms, such as nitrogen, sulfur, oxygen and selenium, such as, for example, a thiazolyl group, a benzothiazolyl group, an oxazolyl group, a benzoxazolyl group, a selenazolyl group, a benzoselenazolyl group, a benzimiazolyl group, a triazinyl group, a pyrimidinyl group, a pyridyl group, a quinolyl group, a thienyl group, etc.; R represents any of the groups represented by R, and, in addition, represents an alkyl group (e.g., methyl, butyl, hexyl, dodecyl, mercaptomethyl, mercaptoethyl, etc.) etc., hydrogen, hydroxyl, carboxyl, a salt of a carboxyl group (e.g., an alkali metal salt or ammonium salt), a carboxy ester group (e.g., methoxycarbonyl, ethoxycarbonyl, phenoxycarbonyl, etc.), an amino group (e.g., amino, ethylamino, dimethylamino, anilino, etc.), a carbamyl group (e.g., carbamyl, ethylcarbamyl, dimethylcarbamyl, phenylcarbamyl, etc.), sulfo, a salt of a sulfo group (e.g., an alkali metal salt), a sulfoamido group (e.g., methylsulfonamido, butylsulfonamido, phenylsulfonamido, etc.), a sulfamyl group (e.g., sulfamyl, methylsulfamyl, butylsulfamyl, phenylsulfamyl, etc.), the mercapto group, the nitro group, or any other substituent cited as being present in this position of the formazan or the tetrazolium salt in Chem. Rev. 55, 355-483 (1955); and the substituents R and R can advantageously contain an electronsharing group capable of forming metal chelates or complexes, such as primary, secondary and tertiary amino, substituted amino, oxime, thioether, keto, thioketo, hydroxyl, mercapto, carboxyl, carboxyl, sulfo, phospho, alkoxy groups or complexes; X represents an anion (e.g., chloride, iodide, bromide, sulfate, paratoluenesulfonate, methylsulfate, ethylsulfate, nitrate, acetate, perchlorate, perborate, sulfite, hydroxide, carbonate, etc.); D represents a divalent aromatic group (e.g., a phenylene, diphenylene, naphthalene, phenylmethylphenyl, etc.); and E represents a divalent group such as an alkylene group (e.g., methylene, ethylene, propylene, butylene, etc.), an arylene group (e.g., phenylene, naphthalene, diphenylene, etc.), an arylene alkylene group, for example, a phenylene alkylene group (e.g., phenylene methylene, phenylene butylene, phenylene hexylene, etc.), a naphthylene alkylene group (e.g., naphthylene methylene, naphthylene butylene, naphthylene propylene, etc.), etc; n represents an integer of from 1 to 5.

Tetrazolium salts used to advantage according to our invention include the following representative compounds:

2,3,5-triphenyl-2H-tetrazolium chloride 2,3,5-tri(p-carboxyethylphenyl)-2H-tetrazolium bromide 2-(benzothiazol-Z-yl)-3-phenyl-S-(o-chlorophenyl)2H- tetrazolium chloride 2-(4,5-dimethylthiazol-2-yl)-3,5-diphenyl-2H-tetrazolium bromide 2,3-diphenyl-2Htetrazolium chloride 2,3-diphenyl-2H-tetrazolium iodide 2,3-diphenyl-5-methyl-2H-tetrazolium chloride 2,3-diphenyl-5-methyl-2H-tetrazolium bromide 3-(p-hydroxyphenyl)-5-methyl-2-phenyl-2H-tetrazolium chloride 3-(o-carboxyphenyl)-5-methyl-2-phenyl-2H-tetrazolium chloride 3-(p-carboxyphenyl)5'mcthyl-2-phcnyl-2H-tctrazolium chloride 3-(p-sulfamylphcnyl)-5-methyl-2-phenyl-2H-tetrazolium chloride 2,3-diphenyl5-ethyl-2H-tetrazolium chloride 3-(p-sulfamylphenyl)-3-phenyl-5-propyl-2H-tetrazolium chloride 2,3-diphenyl-S-isobutyl-ZH-tetrazolium chloride 2,3-diphenyl-S-n-hexyl-ZH-tetrazolium chloride 2-phenyl-3-(p-sulfamylphenyl)-5-hexyl-2H-tetrazolium chloride 2,3-diphenyl-5-dodecyl-2H-tetrazolium chloride 2,3-diphenpl-5-hydroxy-2H-tetrazoliurn betaine 2,B-diphenyl-5hydroxy-2H-tetrazolium chloride 2,3-diphenyl-5-mercapto-2H-tetrazolium betaine 5-amino-2,B-diphenyI-ZH-tetrazolium chloride 5-benzamido-2,3-diphenyl-2H-tetrazolium chloride 5-benzamido-2,3-diphenyl-ZH-tetrazolium betaine 5-cyano-2,3-diphenyl-2H-tetrazolium chloride 5-carboxy-2,3diphenyl-2H-tetrazolium betaine 5-carboxy-2,3-diphenyl-2H-tetrazolium chloride 5-carboxy-2,3-diphenyl-2H-tetrazolium nitrate 3-(benzothiazol-2-yl )-5-( 4-hexoxyphenyl )-2-( 3-sulfophenyl)-2H-tetrazolium Z-benzothiazol-Z-yl)-3-phenyl-5[4-( 3,5-disulfobenzamido) phenyl]-2H-tetrazolium bromide (disodium salt) 2-(benz0thiazol-2yl)-5-(2-chlorophenyl)-3-(4-nitrophenyl)-2H'tetrazolium bromide 2-(benzothiazol-Zyl)-5-phenyl-3-(4-tolyl )-2H-tetrazolium bromide 2-(benzothiazol-Z-yl)-3-(4-chlorophenyl)-5-phenyl-2H- tetrazolium bromide 2-(benzothiazol-2-yl)-5-(4-chlorophenyl)-3-(4-nitrophenyl)-2H-tetrazolium bromide 5-ethoxycarbonyl-2,3-diphenyl-2H-tetrazolium chloride 5-ethoxycarbonyl-2,3-di(3-nitrophenyl)-2l-l-tetrazolium chloride 5-carboxy-2,3-di(p-hydroxyphenyl)-2H-tetrazolium betaine 5-carboxy-2,3-di(p-ethoxyphenyl)-2H-tetrazolium chloride 2,3-di-(p-ethoxyphenyl)-5-ethoxycarbonyl-ZH-tetrazolium chloride 5-acetyl-2,3-diphenyl-2l-l-tetrazolium chloride 5-benzoyl-2,3-diphenyl-2H-tetrazolium chloride 2,5-diphenyl-3-(p-tolyl)-2H-tetrazolium bromide 2,5-diphenyl-3-(p-isopropylphenyl)-2H-tetrazolium mide 2,5-diphenyl-3-(p-n-dodecylphenyl)-2l-l-tetrazolium iodide 2,5-diphenyl-3-(p-diphenyl)-2H-tetra2olium chloride 2,3-diphenyl-5-(p-diphenyl)-2l-l-tetrazolium chloride 2,5-diphenyl-3-(p-chlorophenyl)-2H-tetra2o|ium iodide 2,5-diphenyl-3-(iodophenyl)-2H-tetrazolium chloride 35 di(p-bromophenyl)-2-phenyl-2H-tetra2olium chloride 5-(p-bromophenyl)-2-phenyl-3-(2,4,6-tribromophenyl ZH-tetrazolium bromide 3-(p-iodophenyl)Q-(p-nitrophenyl)-5-phenyl-2H-tetrazolium chloride 3-(p-hydroxyphenyl)-5-(p-nitrophenyl)-2-phenyl-2H- tetrazolium chloride 5-( 3,4-dimethoxyphenyl)-3-methoxyphenyl-Z-phenyl-ZH- tetrazolium iodide 5-( 3-methoxyphenyl)-3-( 3-trifluoromethylphenyl )-2-phenyl-2H-tetrazolium acetate 2-(3-carboxyphenyl)-3,5-diphenyl-2H-tetrazolium iodide 5-(4-cyanophenyl)-2,3-diphenyl-2H-tetrazolium chloride 2,3-diphenyl-5-sulfophenyl-2H-tetrazolium betaine 3-(p-aminophenyl)-2,5-diphenyl-2H-tetrazolium chloride 3-(p-acetamidophenyl)-2,5-diphenyl-2H-tetrazolium chloride 5-(4-aminophenyl)-2,3-diphenyl-2H-tetrazolium chloride 5-acetyl-2,3-diphenyl-2H-tetrazolium chloride 2,3-diphenyl-5-(4-phenylsulfamylphenyl)-2H-tetrazolium hydroxide 3-(4-amino-3-chlorophenyl)-2,S-diphenyI-ZH-tetrazolium chloride 3-(4-amino-2-nitrophenyl )-2,5-diphenyl-ZH-tetrazolium chloride 3-(4-amino-3-hydroxyphenyl)-2,S-diphcnyl-ZH-tetrazolium chloride 2,5-diphenyl-3-(4-octadecylaminophenyl)-2H-tetrazolium chloride bro- 3aminododecylaminophenyl-2,5diphenyl-ZH-tetrazolium chloride 2,5-diphenyl-3-( 4-N-trimethylammoniumphenyl )-2H- tetrazolium methylsulfate 3-( 2-benzyloxyphenyl)-5-(4-N-trimethylammoniumphenyl)2-phenyl-2l-l-tetrazolium chloride 5-(fur-2-yl)-2,3diphenyl-Zl-l-tetrazolium chloride 5-(fur-2-yl)-3-(4-chlorophenyl)-2-quinol-2-yl)-2l-ltetrazolium acetate 5-( thien-Z-yl )2,3diphenyl-2H-tetrazolium chloride 2,3-diphenyl-5-( pyrid-Z-yl )-2H-tetrazolium bromide 2 ,3-diphenyl-5-(pyrid-4 yl)-2H tetrazoliunrchloride 5,5'-dimethyl-3,3diphenyl-Z,2-di-p-diphenylene di-(2H- tetrazolium chloride) 3 ,3 ,5 ,5 -tetraphenyl-2,2 -di-p-( 3 ,3 '-dimethyl-diphenylene di-( 2H-tetrazolium chloride 3,3-diphenyl-5,5di(thien-2-yl)-2,2'-dl-p-(3,3-di-methoxydiphenylene) di-( ZH-tetrazolium chloride) 3,3,5,5-tetraphenyl-2,2syn-p-phenylthiourea tetrazolium chloride) 3,3,5,5-tetraphenyl-2,2syn-p-phenyl sulfoxlde (Ii-(2H- tetrazolium chloride) 2,2,3,3' tetraphenyl-5,5'-p-phenylene ethylene di-( 2H- tetrazolium chloride) 2-( benzothiazol-Z-yl )-5-( 4-acetamidophenyl)-3-( 4-phenylazophenyl)-2H-tetrazolium bromide 2-( benzothiazol-Z-yl )-3-( 4'methoxyphenyl )-5 -phenyl-2H- tetrazolium bromide 2-( 4,5 dimethylthiazol-2-yl )-3 5-diphenyl-ZH-tetrazolium bromide 2-(4-chlorophenyl)-3-(2-chlorophenyl)-5 -(Py id-2-yl)-2H- tetrazolium acetato 2,3diphenyl-S-(quinol-Z-yl)-2H-tetrazolium bromide 2-(benzimidazol-2-yl)-5-( 2-chlorophenyl)-3-phenyl-2H- tqt a o u r ds .7 5-(2-chlorophenyl)-3-phenyl-2-(thien-2yl)-2H-tetrazolium chloride 3,5-diphenyl-2-(pyrid-2-yl )-2H-tetrazolium chloride 3,5-diphenyl-2-(triazin-2-yl)- ZH-tetrazolium chloride U I These tetrazolium salts are well known in the art, most of them having been described in literature references such as Chemical Revue 55, published bimonthly for the American Chemical Society by the Williams and Wilkins Co., Baltimore, 1955. Any tetrazolium salts that are not shown specifically in the prior art are advantageously prepared by methods well known i n the art. V When aqueous solutions of our T-salts, brought into contact with metal images of palladium or any metal more easily oxidized (i.e., has a standard oxidation potential more positive than 0.98 volt) (e.g., silver, nickel, copper, iron, palladium, zinc, lead, tin, etc.), the metal is oxidized to its ion and the T- salt is reduced to produce the corresponding formazan dye. The following equation shows a typical reaction.

Any ligand that is a silver complexing agent is advantageously used that produces a silver ion complex with a cumulative equilibrium constant B i.e.,

(concentration of silver ion complex) a (concentration of silver ion) X (concentration of complexing agent) that is smaller than the [3 for the silver complexed with cyanide ion in a given solvent system at about 20 C. The 3, constants used herein are measured with a silver electrode in contact with a solution (at 20 C.) of the complexing agent to which is being added silver ions as is described in Stability Constants of Metal-Ion Complexes," in Special Publications No. 17, published in London by The Chemical Society in 1964. This reference cites numerous cumulative equilibrium constants that are measured in an aqueous medium, except when the complexing agent doesnt have the desired solubility in water, then a solvent or solvent mixture is used in which both complexing agent and complex are soluble, the tests being the same as in other instances where the complexing agent is water-soluble. Metal images other than silver are also advantageously converted for formazan dye images. Preferably, a silver complexing agent is employed that produces with silver a complex with a B value that that is less than about l0 which is about 10" times smaller than the B of 10 for silver ions complexed with cyanide ions. By a diffusible metal complex, we mean a metal complex that in water solution can pass freely through photographic silver halide emulsion layers. Included among the ligands used to advantage are the following typical examples: water-soluble thiosulfates (e.g., sodium thiosulfate, potassium thiosulfate, ammonium thiosulfate, etc.), thiourea, ethylenethiourea, a water-soluble thiocyanate (e.g., sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate), a water-soluble sulfur containing dibasic acid. Water-soluble diols used to advantage include those having the formula:

wherein p is an integer of from 2 to 13; the 2's represent oxygen or sulfur atoms such that at least one-third of the Z atoms are sulfur and there are at least two consecutive Zs in the structure of the compound which are sulfur atoms. The diols advantageously used are also included in compounds having the formula:

wherein X and X represent oxygen or sulfur, such that when X represents oxygen, X represents sulfur and when X represents sulfur, X represents oxygen; c, d, e, f and g each represent an integer of from 1 to 15, such that the sum of c-l-d-i-efl-g represents an integer of from 6 to 19, and such that at least one third of the total of all the Xs plus all the X"s represent sulfur atoms and at least two consecutive X's and/or X"s in the structure of the compound are sulfur atoms.

Typical diols include the following:

1. 3,6-Dithia-l ,8-octanediol ..EQQHQHZSCBZ ZS HZ 2 2. 3,6,9-Trithial ,1 l-undecanediol iQQBZQHZ C Z H HZS HZQ Z H 4. 9-Oxa-3,6,9,12, lS-tetrathial l 7-heptadecanediol 5. 9, l 2-Dioxa-3 ,6, l 5 l 8-tetrathial ,20-eicosanediol 8. 3,1 8-Dioxa-6,9,l2,15-tetrathia-l ,20-eicosanediol HOCH Cl-l (Cl-l CH S ).,Cl-l CH OCl-l CH OH 9. 12,18-Dioxa-3,6,9,l5,2l,24,27-heptathia-l,29-

nonacosanediol HO(CH CH S) CH CH OCH CH SCH CH O(CH CH S),-,CH CH OH 10. 6,9, l 5,18-Tetrathia-3, l 2,2 l-trioxa-l,23-tricosanediol HOCH CH O(CH CH S) CH Cl-I O(CH CI-l S) CH CH OCH CH Water-soluble sulfur containing dibasic acids used to advantage include those having the formula:

HOOCCH (SCH CH2)qSCH CO0l-t in which q represents an integer of from 1 to, and including, 3

and the alkali metal and ammonium salts of said acids. Typical illustrative examples include:

ethylene-bis-thioglycolic acid 3,6,9-trithiahendecanedioic acid 3,6,9, 1 2-tetrathiatetradecanedioic acid ethylene-bis-thioglycolic acid disodium salt ethylene-bis-thioglycolic acid dipotassium salt ethylene-bis-thioglycolic acid diammonium salt 3,6,9-trithiahendecanedioic acid disodium salt 3,6,9, 1 2-tetrathiatetradecanedioic acid disodium salt The concentration of the T-salt and the ligand in our compositions can be varied considerably, with an operable range of concentrations extending from the solubility limit of the T- salt and the solubility limit of the ligand down to a minimum concentration where the overall reaction potential for the specific T-salt, ligand and specific metal image just remains positive, usually above +0.01 volt. The operable concentration ranges and the preferred concentration ranges are readily determined by methods well known in the art and need not be discussed further.

The metal images that are advantageously treated with our T-salt ligand compositions are produced by any of the conventional image-forming methods and especially by photographic methods, using chemical developing-out materials, physical developing-out materials, etc. The metal image is advantageously made up of minute particles of metal in a binder, e.g., a hydrophilic colloid such as, gelatin or gelatin substitute, or made ofa solid, continuous surface of metal.

The following examples are included for a further understanding ofour invention:

Example 1 Conversion of a Silver Image to a Formazan Dye Image A sample of a supported negative type, developing-out, single-layer fine-grain gelatinous silver chlorobromide emulsion, having been exposed to a graduated-density test object, blackand-white developed in a conventional aqueous alkaline pmethylaminophenol and hydroquinone developer solution, fixed in a conventional alkali metal thiosulfate fixing bath, washed and dried, is treated for 4 minutes at 75 F. in Solution A (see composition below), washed and dried. Solution A is made by dissolving the following composition:

in 600 ml. of water, then bringing the total volume to 1 liter. Solution A has a pH of 7. Sensitometric curves of the images in'the sample before and after treatment in-Solution A show a pronounced increase in image density obtained by the conversion of a metallic silver image to formazan dye by a solution according to our invention. The )tmax of the formazan dye is 490 Ill/L. Example 2 pH-lndependence and Solution Stability Three samples of a negative type developing-out fine-grain gelatinous silver bromoiodide emulsion coated film, each having been flash-exposed, black-and-white developed to a neutral density of 0.7 in a conventional bIack-and-white developer as used in Example 1, fixed in a conventional alkali metal thiosulfate fixing bath, washed and dried, are treated for 2 minutes at F. in portions of Solution B (see formula below) whose pH values are 4.3, 6.1, and 10.0, respectively. The samples are subsequently washed and dried. The dye densities in the three samples are essentially the same, as is shown in Table l. The solutions are kept for 96 hours at room temperature and then used to repeat the above procedure with three similar samples. Essentially the same dye densities are obtained. Solution B is made by dissolving a composition containing l of 2,3,5 ,-triphenyl-ZH-tetrazolium chloride and 10 g. of ammonium thiosulfate in water to make 100 ml. of solution.

image to a formazan dye image by a procedure according to our invention is effectively accomplished over a wide range of pH conditions. Example 3 Spectral Distribution of the Light Absorption of Image Formazan Dye vs. Image Silver A sample of the silver halide emulsion coated film described in Example 2 is flash-exposed, black-and-white developed, fixed, washed and dried as described in Example 2, The density of the silver image to red, green and blue light is recorded under Untreated Area" in Table 2. Upon treatment of the sample for 60 minutes at 75 F. in Solution C (see composition below), the initial silver image is converted to a brown formazan dye image whose density to red, green and blue light is recorded under Treated Area in Table 2. Solution C is made by dissolving a composition containing 1 g. of 2- (benzothiazol-2-yl)-3-phenyl-5-(o-chlorophenyl)-2H- tetrazolium bromide and 10 g. of ammonium thiosulfate in water to make 100 ml. of solution having a pH of 10.

The above data illustrate that a silver image of a given spectral density is effectively converted to a formazan dye image having an overall higher spectral density. Example 4 Mixtures of T-salts Are Used To Adjust Color Of Dye Image Four samples of the silver halide emulsion coated film described in Example 2, having been flash-exposed, blackand-white developed, fixed, washed and dried as described in Example 2, are treated for 2 minutes at 75 F. in Solution B (pH 8, described in Example 2) and in Solution D (described below) and in mixtures thereof as shown in Table 3. The obtained formazan dye images range in color from red to blue.

Their spectral absorption to the red, green and blue regions of the visible spectrum is illustrated in Table 3. Solution D is made by dissolving a composition containing 1 g. of 2- (4,5dimethylthiazd-2-yl)-3,5-diphenyl-2H-tetrazolium bromide and 10 g. of ammonium thiosulfate in water to make 100 ml. of solution having a pH of 8.0.

Example 5 Silver Images In A Variety Of Photographic Materials Are Convertible'To Formazan Dye Images Black-and-white processed (i.e., developed, fixed, washed and dried as described in Example 1) samples of several types of negative type, developing-out photographic materials are treated from I to 16 minutes in portions of Solution B (see Example 2) ranging in pH from 6 to 12 to produce formazan dye images essentially as described in the preceding examples. The photographic materials include:

I. A coarse-grain gelatinous silver bromoiodide X-ray film 2. A fine-grain gelatinous silver bromoiodide film 3. Supported gelatinous layers containing Carey Lea silver,

and 4. Several fine-grain gelatinous silver bromoiodide emulsion coated Micro-File films (Kodak Trademark) The results show our Solution B is an active Blix for removing silver from photographic layers. The density and spectral absorption characteristics of the formazan dyes to which the silver is converted during the above treatments in Solution B are similar to the values cited in the preceding examples. Example 6 Electron Transfer Catalyst Accelerates Rate Of Dye Formation Two black-and-white processed (i.e., developed, fixed, washed and dried as described in Example 1) samples of the X-ray film described in Example 5 are treated at 75 F. and pH l0.0 for 2 and minutes, respectively, in Solution B (see Example 2). Two other samples are similarly treated, except that 2 g. of the electron transfer agent N,N,N', N-tetramethyl-pphenylenediamine hydrochloride, are added to a 100-ml. portion of Solution B. The density of the formazan dye images in the two samples treated in the presence of the electron transfer agent is higher than the density in the samples treated in Solution B not containing the agent. This observation illustrated by the data in Table 4.

Table 4 Red tg Green Blue Solution 8, 2 min. 0.64 0.61 0.54 Solution B plus agent, 2 min. 0.79 0.80 0.66

- Solution B, 10 min. 0.7l 0.79 0,70 Solution 8 plus agent. l0 min. 0.84 1.02 0.82

Example 7 Certain Organic Solvents Increase Rate Of Dye Formation Two black-and-white processed (i.e., developed, fixed, washed and dried as described in Example 1) samples of a negative type, developing out fine-grain gelatinous silver chlorobromide emulsion Micro-File films are treated at 115 F. and pH 7.0 in Solutions E and F (compositions below), respectively, for 0, 15, 30, 60 and 120 seconds. The data recorded in Table 5 indicate that benzyl alcohol increases the rate of the conversion from image silver to formazan dye. Solution E is made by dissolving a composition containing 1 g. of 2,3,5-triphenyl-2I-I -tetrazolium chloride, 20 g. of ammonium thiosulfate and 0.1 g. of thiourea in water to make ml. of solution. Solution F is made by adding 0.4 ml. of benzyl alcohol to 100 ml. of Solution E.

Table 5 mg. of AG/ft. Remaining in Film after Treatment 0 sec. l5 sec. 30 sec. 60 sec. sec.

Solution E 180 30 l7 15 Solution F I80 46 l4 l0 8 Example 8 Mixtures of Metal Complexing Agents Increase The Rate Of Dye Formation A first sample of a sensitometrically exposed, developed, fixed, washed and dried, negative type, developing-out, finegrain gelatinous silver bromoiodide emulsion coated film is treated at 75 F. for 2 minutes in Solution G (see composition below). Solution G is made by dissolving the following composition:

2,3,5-tri henyl-ZH-tetrazolium chloride 1 g. l\I|-|, ,s,o 10 g. Disodium phosphate 1 g. Benzyl alcohol 0.8 ml. Ethylene thiourea 0.0l g.

in water to make I00 ml. of solution. A second and a third sample are treated similarly except that Solution G contained O.l g. and 1.0 g. of ethylene thiourea, respectively. The increase in the rate of conversion of silver to formazan dye with increased concentration of a second silver complexing agent, such as ethylene thiourea, is illustrated in Table 6.

Table 6 Photographic Materials Increases With Increased Temperature A selectively balanced Blix composition according to our invention effectively removes the image silver from various types of processed photographic materials. The rate of silver removal increases with increased temperature. Silver images in several exposed, developed, fixed, washed and dried coarsegrain gelatinous silver halide X-ray films and a fine-grain gelatinous silver halide film are treated for various times at temperatures of 75 F., 100 F. and F. in portions of Solution B (see Example 2). These films are coated with negative type, developing out gelatinous-silver bromoiodide emulsions. The effect of temperature on the rate and amount of silver removal is illustrated by the data recorded in Table 7.

TABLE? Mg. Ag/tt. remalnlng in film after treatment in Bolu ion B for-- Temr Photognmaterlal 0min. 1min. 4111111. 8 min. 16 min.

' 75 so 60 as 26 20 An X-ray film 100 80 34 20 14 12 2 LL i3. .22. Walt! 0 TABLE 7 Mg. Jig/it. remaining in Illru alter treatment in Solution B (or-- 'lomp., Photogr. material F. min. 1 min. 4 min. 8 min. 16 min.

75 205 275 220 170 90 A black-and-whito fllm 100 295 280 134 104 64 125 295 216 40 30 18 76 112 102 68 52 50 A second X-ray film 100 112 76 (S0 50 2 126 112 54 8 0 76 88 68 38 34 30 A third X-ray film 100. 88 34 32 30 24 125 88 34 24 10 0 Similar results are obtained when a developed (but un- TABLE 9 bleached and unfixed) multicolor, multilayer color film is blixed with our composition. Example l0 Formazan Dye images Are Sharper Than the initial Silver Images From Which They Are Derived time in A sensitornetrically exposed negative type, developing-out 2Q H coarse-grain gelatinous silver bromoiodide X-ray film is developed, fixed washed and dried as described in Example 1. One sample of this processed film is used as a control: a s 2min: 1,; second sample is treated for 4 minutes in Solution G (see Ex- Sample 4 4 min. 3.20 o. lb 2.0 ample 8) and a third sample is treated for 8 minutes in Solu- Sample 5 tion 0. The densities of the resulting images to blue light in each of the processed film samples are measured with a densitometer. The density data for the first, ninth and l7the steps mpl 12 C n rsi n of Nickel and Copper Images T0 of the sensitometric images are listed in Table 8 below: Formazan Dye Images A. A first sample of a nickel image reproduction prepared T l 8 by physically developing an exposed photosensitive material of the type containing a layer of palladium nuclei on a Ti0 coated support, described in Examples 15 and I7 on pages 18 and 19 of Belgian Pat. No. 718,019, is treated for 5 minutes at TrcatmcntTime en i y t Blu Light a 75 F. in Solution A (see Example I), washed and dried. A

Film mp9 second sample containing an identical nickel image is not treated in a Blix solution and served as a control. A comgss r' 8%; l'ig 1'28 parison between the sensitometric curves of the nickel image 3 8 in the untreated sample and the formazan dye image in the treated sample demonstrates the effective conversion of nickel to formazan dye in the blix solution according to our invention.

B. A copper image is similarly treated with essentially the same result. Example 13 A Soluble-dye-forming T-salt Blixes Image These data show the increase in image density produced by treatment of film samples with Solution G. X-ray line exposures made on Film Samples 4, 5 and 6 as described in Rev. of 45 Scientific Instruments, 38, No. 11 pages l.6l9-1,622, Nov. 19, 1967 are processed as described for Samples 1, 2 and 3, Save w'thout Retfmtmn ofa Dye Image respectively, in this example. Microdensitometric traces of the A bkfck'and'whlle P 0 ample of a negative type, resulting images indicate the formazan dye images in Film developmg out finegram gelatinous Sliver Promolodlde Samples 5 and 6 are sharper than the ii image i Sample 4 coated film is treated in Solution I (see composition below) at Example I l Silver Images In Direct Reversal Emulsions Are I is made y dissolving 2 2- Of (P' Effectively Converted to Formazan Dye Images boxyethylphenyl)-2H-tetrazolium bromide and 20 g. of ami i i monium thiosulfate to make 100 ml. ofsolution having a pH of 7.0. The treated sample is subsequently washed and dried. An 1 inspection of the dried sample shows that it is substantially free of silver and free of formazan dye.

Example 14 The Forrnazan Image Dyes Generated By the Five samples of a coating of a direct-positive type, developing-out, gelatinous silver chlorobromoiodide emulsion are exposed to a graduated density test object and black-and-white developed to a direct positive image reproduction. "max,

"min, and gamma of the sensitometric curve (Le, a curve of image density exposure) representing the image in one of Method According to Our Invention Can Be Chelated to lm the samples are recorded in Table 9. The remaining four sam- Prove the Dyes Stability and To Shift Their Spectral 'l ples are subsequently treated at 75 F. for l, 2, 4 and 8 Peaks I minutes, respectively, in Solution H (see composition below). A first Sample of a "egatwe yp developmg'out -g soiuiion H is made by dissolving the f n i i i gelatinous silver bromoiodide emulsion coated film is flash-exposed, black-and-white developed to a silver density of 0.4

fixed, washed and dried. A second sample is similarly Nu HPO 1 gmimlsa'ofl 20 8, processed and subsequently treated for 3 minutes at F. m Thiourcu l 5- Solution .l (see composition below), washed and dried. Solu- Benzylulcohol 0.4 ml. zjsmphenymwmmnfium tlon J is made by dlSSOlVll'lg the following composition.

chloride l g.

- 70 2,5-diphenyl-3-(4,5-dimethylthiazol-2-yl)- in water to make ml. of solution of pH 7.0. "max, "min, :iz g gg 0 I g 5 0 ml and gamma of the sensitometric curves (read through a green 10% (101520, 50mm, 200 mi filter) representing the corresponding fonnazan dye images, i I are recorded in Table 9. in water to make 45 ml. of solution having a pH of 8.0. Two

13 additional samples are similarly processed and treated in separate preparations of Solution J which contained, instead of the ml. of water, 20 ml. of 10 percent solutions of the metal ions as shown in Table ll. The spectral absorption peaks (Amax) of the formazan dyes generated in the above samples are recorded in Table 10.

A composition is made like that in Example 2, but in which the ammonium thiosulfate is replaced by an equimolar amount of sodium thiosulfate. Examples 1 and 9 are then repeated, using the modified solution. Results are obtained that are similar to those obtained in Examples l and 9.

EXAMPLE l6 Examples 2 and 9 are repeated, but using in place of Solution B, a solution made by replacing the ammonium thiosulfate with an equimolar amount of ammonium thiocyanate. Similar results to those in Examples 2 and 9 are obtained.

EXAMPLE 17 Examples 2 and 9 are repeated, but using in place of Solution A, a solution made by replacing the ammonium thiosulfate with an equimolar amount of 3,6-dithia-l,8-octanediol. Results similar to those of Examples 2 and 9 are obtained.

EXAMPLE 18 An X-ray film like that described in Example 10 is exposed to an X-ray image, developed in a conventional X-ray film developer, fixed, washed and dried. Fifteen identical samples are taken of the processed X-ray film. One sample is used as a control, while the other samples are each treated by contacting with a different Solution K, L, M, N, O, P, Q, R, S, T, U, V and W (described below). The silver image in each of the treated samples is replaced by a formazan dye image corresponding to the particular T-salt used in the treatment solution of our invention. Solutions K through W are made, each containing 10 g. of ammonium thiosulfate per 100 ml. and l g. of the T-salt indicated in the table below:

Solution T-salt K 2,3-diphenyl-i-(pyrid-Z-yl)-2H-tetrazolium bromide L 2,3-diphenyl-5-( benzoxazol-2-yl)-2H-tetrnzolium chloride M 2,3di( 4-bromophenyl)-S-( benzothiuzol-Lyl )-2H Example 19 A multilayer, multicolor photographic film having a redsensitized negative-speed gelatino-silver bromoiodide emulsion layer containing a nondiffusible phenolic cyan-dye-forming coupler that was incorporated with a low-boiling solvent (e.g., ethyl acetate), a green-sensitized negative-speed gelatino-silver bromoiodide emulsion layer containing a nondiffuslble S-pyrazolone magenta-dye-forming coupler that was incorporated with ethyl acetate as solvent, and a blue-sensitive negative-speed gelatino-silver bromoiodide emulsion containing a nondiffusible acetoacetanilido yellow-dye-forming coupler that was incorporated with ethyl acetate as the coupler solvent is sensitometrically exposed and color processed as described in Example 2, Column 12 of US. Pat. No. 2,944,900 up to the bleach and fix steps, which are replaced by contacting the developed and washed film with Blix solution described in our Example 13. The blixed film is then washed and dried, leaving the color reproduction made of dyes formed from the incorporated couplers in the color development step and essentially no residual silver.

This patent application is being filed simultaneously with another patent application in our names which describes and claims a related invention of ours that is concerned with replacing a metal image with a formazan dye image by contacting the metal image with a solution of a T-salt that contains at least one complexing moiety (on T-salt) that complexes metal so that no external source of complexing agent is required as is required in our invention described and claimed in the immediate patent application. A a

The invention has been described in detail with particular reference to preferred embodiments thereof, but, it will be understood that variations and modifications can be efiected within the spirit and scope of the invention.

We claim:

1. A photographic composition for converting a zero valent metal image into a formazan dye comprising (a) a soluble and diffusible tetrazolium salt and (b) a ligand which produces a silver complex having a smaller cumulative equilibrium constant of [3 than the complex of silver with cyanide ion, such that the combination of said tetrazolium salt and said ligand with a zero valent metal image in the presence of water produces a solution reaction potential of at least +0.01 volt.

2. A photographic composition for converting a zero valent metal image into a formazan dye comprising (a) a water-soluble, diffusible tetrazolium salt represented by the formulas:

wherein R and R each represent a group selected from the class consisting of an aryl group and a heterocyclic group; R represents a member selected from the class consisting of hydrogen, an alkyl group, an aryl group, a heterocyclic group, hydroxyl, carboxyl group, salt of carboxyl group, a carboxyester group, an amino group, a carbamyl group, sulfo, a slat of the sulfo group, a sulfonamido group, a sulfamyl group, the mercapto group and the nitro group; X represents an anion; D represents a divalent aromatic group and E represents a divalent group selected from the class consisting of an alkylene group, an arylene group and an aralkylene group; n represents an integer of from 1 to 5; and (b) a metal complexing agent which produces a silver complex having a cumulative equilibrium constant [3 that is at least 10 times less than said constant for the complex of silver with cyanide ion, such that the combination of said tetrazolium salt and said complexing agent with a zero valent metal image in the presence of water produces a solution reaction potential of at least +0.01 volt.

3. A composition of claim 2 in which the metal complexing agent is selected from the class consisting of a water-soluble thiosulfate, thiourea, ethylenethiourea, a water-soluble thiocyanate, a water-soluble sulfur containing dibasic acid and a water-soluble diol containing sulfur atoms.

4. A composition of claim 2 in which the tetrazolium salt is 2,3,S-triphenyl-ZH-tetrazolium chloride.

5. A composition of claim 2 in which the tetrazolium salt is 2,3,5-tri( p-carboxyphenyl)-2H-tetrazolium bromide.

6. A composition of claim 2 in which the metal complexing agent is a water-soluble thiosulfate.

7. A photographic composition comprising 2,3,5-triphenyl- ZH-tetrazolium chloride and ammonium thiosulfate, which combination with a zero valent metal image in the presence of water produces a solution reaction potential of at least +0.01 volt and which metal complexes are water soluble and diffusible.

8. A photographic composition comprising 2,3,5-tri(p-carboxyethylphenyl)-2l-l-tetrazolium bromide and ammonium thiosulfate which combination with a zero valent metal image in the presence of water produces a solution reaction potential of at least +0.01 volt and which metal complexes are water soluble and diffusible.

9. A photographic composition comprising 2-(benzothiazol- 2-yl)-3 -phenyl-5-(o-chlorophenyl)-2H-tetrazolium chloride and ammonium thiosulfate, which combination with a zero valent metal image in the presence of water produces a solution reaction potential of at least +0.01 volt and which metal complexes are water soluble and difi'usible.

10. A photographic composition comprising 2-(4,5- dimethylthiazol-Z-yl)-3,5-diphenyl-2H-tetrazolium bromide and ammonium thiosulfate, which combination with a zero valent metal image in the presence of water produces a solution reaction potential of at least +0.01 volt and which metal complexes are water soluble and diffusible.

11. A process for converting at least a portion of a zero valent metal image to a formazan dye image which comprises contacting said metal image with a water-soluble, diffusible ligand that forms a silver complex with a smaller cumulative equilibrium constant B than the complex of silver with cyanide ion, such that the combination of said metal, said tetrazolium salt, said ligand and water produces a solution reaction potential of at least +0.01 volt.

12. A process of converting at least a portion of a zero valent metal image to a nondiffusible formazan dye image which comprises the step of contacting said metal image with an aqueous solution containing l) a water-soluble, diffusible tetrazolium salt represented by the formulas:

wherein R, and R each represent a group selected from the class consisting of an aryl group and a heterocyclic group R represents a member selected from the class consisting of hydrogen, an alkyl group, an aryl group, a heterocyclic group, hydroxyl, carboxyl group, salt of carboxyl group, a carboxyester group, an amino group, an amido group, a carbamyl group, sulfo, a salt of the sulfo group, a sulfonamido group,.a sulfamyl group, the mercapto group and the nitro group; X represents an anion; D represents a divalent aromatic group and E represents a divalent group selected from the class consisting of an alkylene group, an arylene group and an aralkylene group; n represents an integer of from 1 to 5; and (2) a metal complexing agent which produces a silver complex that has a cumulative equilibrium constant {3 that is at least 10 times smaller than said constant for the complex of silver with cyanide ion, such that the combination of said aqueous solution with said metal image produces a solution reaction potential of at least 0.01 volt.

13. A single-step photographic process for converting at least a portion of a zero valent metal image in a hydrophilic colloid layer to a nondiffusible formazan dye image, said process comprising the step of contacting said metal image with an aqueous solution containing (1) a water-soluble, diffusible tetrazolium salt and (2) a metal complexing agent which produces a silver complex having a cumulative equilibrium constant B that is at least 10" times smaller than said constant for the complex of silver with cyanide ion, such that the combination of said aqueous solution with said zero valent metal produces a solution reaction potential of at least +0.01 volt.

14. A process of claim 11 in which the formazan dye image formed is nondiffusible.

15. A process of claim 11 in which the formazan dye is diffusible.

16. A process for converting a silver image in a gelatin layer to a formazan dye image and removing silver and silver salts comprising the step of contacting said silver image with an aqueous solution containing 10 g. of 2,3,5-triphenyl-2H- tetrazolium chloride and 200 g. of ammonium thiosulfate per liter of solution.

17. A process for converting a silver image in a gelatin layer to a formazan dye image and removing silver and silver salts comprising the step of contacting said silver image with an aqueous solution containing 10 g. of 2,3,5-triphenyl-2H- tetrazolium chloride, g. of ammonium thiosulfate, 10 g. of disodium phosphate, 0 to 0.8 ml. of benzyl alcohol, 0 to 0.1 of ethylene thiourea, 0 to 10 g. of thiourea per liter of solution.

18. A process for converting a silver image in a gelatin layer to a formazan dye image and removing silver and silver salts comprising the step of contacting said silver image with an aqueous solution containing 3-phenyl-5-(o-chlorophenyl)- ZH-tetrazolium chloride and 100 g. of ammonium thiosulfate per liter of solution.

19. A process for converting a silver image in a gelatin layer to a formazan dye image and removing silver and silver salts comprising the step of contacting said silver image with an aqueous solution containing 10 g. of 2-(4,5-dimethylthiazol-2- yl)-3,5-diphenyl-2H-tetrazolium bromide and 100 g. of ammonium thiosulfate per liter of solution.

20. A process for converting a silver image in a gelatin layer to a formazan dye image and removing silver and silver salts comprising the step of contacting said silver image with an aqueous solution containing 1 g. of 2,3,5-triphenyl-2H- tetrazolium chloride, 0.2 g. of 2-(4,5-dimethylthiazol-2-yl)- 3,5-diphenyl-2H-tetrazolium bromide and 12 g. of ammonium thiosulfate per ml. of solution.

.wgg UNITED STATES PATENT OFFICE 3 CERTIFICATE OF CORRECTION Patent No. 3, L L7 Dated b u y 5, 97 Inventor-(5) Albert T. Brault and Vernon L. Bissonette It is certified that error appears in the tabove-identifiedpatent and that said Letters Patent are hereby corrected as shown below:

' Column 2, line 35, that part of formula reading:

.059 I i should read .059 v v (1" I lines hl -h2, "d represents the number of electrons transferred in said reaction; should be deleted; line 55, after formulas should read Column 3, line I, "Carboxyeth'ylphenyl" should read --carboXyethylphenyl--; line 13, "hereto" should read 1 -hetero--; line hO, "carboxyl, (second occurrence) "should be deleted.=

Column L line 8, that part of formula reading "diphenpl" should read --diphenyl---'; line 9, that part of formula reading "Shydroxy" should read -5-h droxy-- line 15, that part of formula reading "2,3diphenyl should read --2,3-diphenyl-'-; line ho, that part of formula beginning with "35-" is not a part of the preceding formula and should have been placed at the beginning of line L1].

Column 5, line 8, that part of formula reading "-2-quinol-2-yl" should read -2- (quinol-2yl) line 2h, that part of formula reading "Ssulfo" should read --5-sulfo--; line 53, "acetato" should read ---a cetate--.

Column 7, line 3, that part of formula reading "CH 0(2" should read --CH O)'; line 3, that part ,of formula rea ing "CH OH" should read j,--CH GH OH- line 16, that part of formula reading :should read --CH OH-'-; line 67,

"Ma HPOLL" should read --1 Ta H;POL

mgr UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIN Patent No. 1 3 M A7 Dated February 5, 97

. lnventofls) Alber T- Brault and Vernon L. B issonette 2 It; is certified that erroriappears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 8,' line 20, after ".I and before "of" should be inserted --g.-. l

Column 9, I line L that part of formula reading h,5dimethylthiazd" should read --L ,5 -dimethy1thiaZ0l'-; line 23, "1 should read -2=-; line 5'1 after "observation", --isshould be inserted; line 57, "tg" should be deleted.

Column 10, line 17, 5'30" should read ---77--; line 17, under heading "30 sec." should-be inserted --30--; line 3O, that part of formula reading "tri henyl" should read -triphenyl; line 52, "v"shouldbe' deleted.

Column 11 line 23, should read line 28, "1 Tthe" should read 7th"; I

Column 12 line 70, "the 0.1 g. should be deleted and --O.| g.-- should be placed :at the right margin of the column above "5.0 ml."

Column 1 line -11 'ite" should be deleted.

Column 1h, line 11 before "described", -I-- should be inserted.

In the Claims:

- Column IL line 3h, "of" (first occurrence) should be deleted; line on, -"slat" should read --salt- (5/69) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIUN Patent No. BJJLL'ZJWB Dated February 15, 19 72- Inventor(s) Albert T. Braulfi and Vernon L. Bissonette 3 It is certified that error; appears inthe above-identified patent and. that said Letters Patent are hereby corrected 'as shown below:

r- Column 15, line L12, before "ligand", --tetrazolium salt and a-- should be inserted; line Lfl, "of" (first occurrence) should read --;or--.

Column '16, line 2, after "group" (second occurrence) should be inserted; line 9, after "group",

should be inserted; line M "0.8" should read --8.---

Signdand sealed this 1st day of May 1973 (SEAL) Attest; v v v EDWARD M. FLETCHER, JR. R B RT O TS HAH Attesting Officer Commissioner offPatents 

2. A photographic composition for converting a zero valent metal image into a formazan dye comprising (a) a water-soluble, diffusible tetrazolium salt represented by the formulas:
 3. A composition of claim 2 in which the metal complexing agent is selected from the class consisting of a water-soluble thiosulfate, thiourea, ethylenethiourea, a water-soluble thiocyanate, a water-soluble sulfur containing dibasic acid and a water-soluble diol containing sulfur atoms.
 4. A composition of claim 2 in which the tetrazolium salt is 2, 3,5-triphenyl-2H-tetrazolium chloride.
 5. A composition of claim 2 in which the tetrazolium salt is 2, 3,5-tri(p-carboxyphenyl)-2H-tetrazolium bromide.
 6. A composition of claim 2 in which the metal complexing agent is a water-soluble thiosulfate.
 7. A photographic composition comprising 2,3,5-triphenyl-2H-tetrazolium chloride and ammonium thiosulfate, which combination with a zero valent metal image in the presence of water produces a solution reaction potential of at least +0.01 volt and which metal complexes are water soluble and diffusible.
 8. A photographic composition comprising 2,3,5-tri(p-carboxyethylphenyl)-2H-tetrazolium bromide and ammonium thiosulfate which combination with a zero valent metal image in the presence of water produces a solution reaction potential of at least +0.01 volt and which metal complexes are water soluble and diffusible.
 9. A photographic composition comprising 2-(benzothiazol-2-yl)-3-phenyl-5-(o-chlorophenyl)-2H-tetrazolium chloride and ammonium thiosulfate, which combination with a zero valent metal image in the presence of water produces a solution reaction potential of at least +0.01 volt and which metal complexes are water soluble and diffusible.
 10. A photographic composition comprising 2-(4,5-dimethylthiazol-2-yl)-3,5-diphenyl-2H-tetrazolium bromide and ammonium thiosulfate, which combination with a zero valent metal image in the presence of water produces a solution reaction potential of at least +0.01 volt and which metal complexes are water soluble and diffusible.
 11. A process for converting at least a portion of a zero valent metal image to a formazan dye image which comprises contacting said metal image with a water-soluble, diffusible ligand that forms a silver complex with a smaller cumulative equilibrium constant Beta 2 than the complex of silver with cyanide ion, such that the combination of said metal, said tetrazolium salt, said ligand and water produces a solution reaction potential of at least +0.01 volt.
 12. A process of converting at least a portion of a zero valent metal image to a nondiffusible formazan dye image which comprises the step of contacting said metal image with an aqueous solution containing (1) a water-soluble, diffusible tetrazolium salt represented by the formulas:
 13. A single-step photographic process for converting at least a portion of a zero valent metal image in a hydrophilic colloid layer to a nondiffusible formazan dye image, said process comprising the step of contacting said metal image with an aqueous solution containing (1) a water-soluble, diffusible tetrazolium salt and (2) a metal complexing agent which produces a silver complex having a cumulative equilibrium constant Beta 2 that is at least 103 times smaller than said constant for the complex of silver with cyanide ion, such that the combination of said aqueous solution with said zero valent metal produces a solution reaction potential of at least +0.01 volt.
 14. A process of claim 11 in which the formazan dye image formed is nondiffusible.
 15. A process of claim 11 in which the formazan dye is diffusible.
 16. A process for converting a silver image in a gelatin layer to a formazan dye image and removing silver and silver salts comprising the step of contacting said silver image with an aqueous solution containing 10 g. of 2,3,5-triphenyl-2H-tetrazolium chloride and 200 g. of ammonium thiosulfate per liter of solution.
 17. A process for converting a silver image in a gelatin layer to a formazan dye image and removing silver and silver salts comprising the step of contacting said silver image with an aqueous solution containing 10 g. of 2,3,5-triphenyl-2H-tetrazolium chloride, 100 g. of ammonium thiosulfate, 10 g. of disodium phosphate, 0 to 0.8 ml. of benzyl alcohol, 0 to 0.1 of ethylene thiourea, 0 to 10 g. of thiourea per liter of solution.
 18. A process for converting a silver image in a gelatin layer to a formazan dye image and removing silver and silver salts comprising the step of contacting said silver image with an aqueous solution containing 3-phenyl-5-(o-chlorophenyl)-2H-tetrazolium chloride and 100 g. of ammonium thiosulfate per liter of solution.
 19. A process for converting a silver image in a gelatin layer to a formazan dye image and removing silver and silver salts comprising the step of contacting said silver image with an aqueous solution containing 10 g. of 2-(4,5-dimethylthiazol-2-yl)-3,5-diphenyl-2H-tetrazolium bromide and 100 g. of ammonium thiosulfate per liter of solution.
 20. A process for converting a silver image in a gelatin layer to a formazan dye image and removing silver and silver salts comprising the step of contacting said silver image with an aqueous solution containing 1 g. of 2,3,5-triphenyl-2H-tetrazolium chloride, 0.2 g. of 2-(4,5-dimethylthiazol-2-yl)-3,5-diphenyl-2H-tetrazolium bromide and 12 g. of ammonium thiosulfate per 120 ml. of solution. 